ON THE DEEP WATER CRUSTACEA OF GREEN LAKE. 



By C. DWIGHT MARSH. 



During the past two seasons I have become interested in the deep 

 water fauna of Green Lake, and have made a large number of collections. 

 While the results may not be particularly striking, I think they are of 

 sufficient interest to warrant the presentation of a short paper on the 

 subject. Because of its depth, Green Lake resembles, in the conditions 

 controlling animal- life, the larger bodies of water, and might be ex- 

 pected to have a fauna somewhat different from that of the shallower 

 lakes. My collections seem to justify this expectation. 



It is only within a few years that it has been deemed worth while to 

 make any investigation of the fauna of deep water. Even after the ex- 

 istence of a very rich pelagic fauna in the oceans was recognized, bodies 

 of fresh water were almost entirely neglected. Now, it is well known 

 that our lakes have a pelagic fauna rich in individuals, if not in species, 

 and a less abundant abyssal fauna. Most of the European lakes have 

 been explored with more or less thoroughness. Especially noticeable is 

 the extended work of Prof. Forel upon Lake Geneva and the smaller 

 Swiss Lakes. 



In this country comparatively little has been done. Since the initia- 

 tory work of Dr. Hoy in Lake Michigan, some twenty years ago, so far 

 as I know, only two persons have published anything on this subject — 

 Prof. S. I. Smith, and Prof. S. A. Forbes. 



The bottom of Green Lake, in the deeper parts, is a fine blue clay, in 

 which are great numbers of ostracod shells and some few shells of mol- 

 luscs. I submitted the molluscs to Mr. C. T. Simpson of the United 

 States National Museum, who tells me that there was nothing of especial 

 interest among them. They were all littoral forms, and, in most cases, 

 probably washed in from shallower water. 



There were also several species of hydrachna, worms, and infusoria, 

 which I have not worked out. The crustacean fauna is extremely 

 abundant, although the number of species is small. 



